1. Technical Field
The present invention relates to an radiographic imaging apparatus, and in particular to a radiographic imaging apparatus provided with a radiation detection panel.
2. Related Art
FPD's (Flat Panel Detectors) that have a radiation sensitive layer disposed on a Thin Film Transistor (TFT) active matrix substrate, detect irradiated radiation, such as X-rays, and directly convert this radiation into radiographic image data expressing the distribution of irradiated radiation amounts are being put into practice. Portable radiographic imaging apparatuses (sometimes referred to below as “electronic cassettes”) that house a panel type radiation detector, such as one of the above FPDs, a control section including a memory section, and a power source section, also being put into practice for storing in the image memory radiographic image data output from the radiation detector. Due to excellent portability, the electronic cassettes can capture images of investigation subjects still lying on a stretcher or bed, and the imaging location can be readily adjusted by changing the position of the electronic cassette. Hence electronic cassettes can be flexibly adopted for cases of image capture for an investigation subject not able to move.
Related to the above, a technique is described in Japanese Patent Application Laid-Open (JP-A) No. 2003-339687 with an object of realizing image capture from plural directions with an expanded surface area of a flat panel sensor, together with portability and ease of handling. In this technique, a structure capable of opening and closing is described of two plates of flat panel sensor that are joined at edges on one side of each, in an image capture apparatus, such as an electronic cassette, having a flat panel sensor.
A technique is described in JP-A No. 2004-173908 with an object to reduce the physical burden on an operative. In this technique, an electronic cassette (image capture section) is separated from an image control section, the electronic cassette is set in a vertical state in the stage of an auxiliary device, and during image capture, by operating a hydraulic cylinder coupled to the stage, the stage (the detection face of the electronic cassette) is raised to the horizontal.
A technique is described in JP-A No. 2009-80103 with an object to reduce the weight of a cassette system. In this technique, a control unit mounted with electronic components, such as an interface circuit section, a cassette control section, and a communication unit, is configured so as to be separable from a cassette having a radiation detector using a connector and cable, and the control unit is separated from the cassette during image capture.
A technique is described in JP-A No. 2000-10220 with an object of protecting a compact, thin, X-ray detection means during carrying and handling. The X-ray image capture apparatus described has a panel case provided with X-ray detection means, and a control case provided with control means, with these two cases configured so as to be rotatably connected.
A radiographic imaging apparatus, such as an electronic cassette, is configured including a large number of electronic components, particularly in the control section and power source section. Since electronic components with high heat generation amount are employed in part, accompanying a rise in internal temperature of the radiographic imaging apparatus due to heat generation from electronic components, problems sometimes arise such as changes to the electrical characteristics of the radiation detector (such as, for example, increase in noise, increase in dark current flow of the TFTs, and the like), and deterioration in the radiation detector (such as, for example, deformation and damage due to the layered structure of the radiation detector with different thermal expansion coefficients for each member, deterioration and delamination of a bonding member due to repeated changes in temperature, crystallization of amorphous selenium accompanying temperature rises for direct conversion type radiation detectors, and the like). In addition, there are occasions when an unpleasant sensation is imparted to an investigation subject due to excessive rise in surface temperature of the radiographic imaging apparatus. In particular, the above problems are even more significant during video image capture, such as in radiographic guidance, where the amount of heat generated is large in comparison to still image capture due to performing continuous image capture (over a long duration). There is a possibility that counter measures need to be taken which themselves lead to an adverse impact on the ease of use, such as, for example, limiting the duration of continuous operation or the like.
To address this issue, JP-A No. 2009-80103 has an object of suppressing changes in structure (crystallization) of amorphous selenium that configures a portion of the radiation detector. There is a proposal to dispose means to cool the radiation detector within the cassette, however, this leads to problems of the configuration of the radiographic imaging apparatus becoming complicated, and a large increase in the power consumption of the radiographic imaging apparatus due to configuring the cooling means. Heat dissipation or cooling of the radiation detector are not really considered in the techniques of JP-A Nos. 2003-339687, 2004-173908 and 2000-10220.
In order to address these problems, a technique might be considered that employs the techniques of JP-A No. 2003-339687 and JP-A No. 2000-10220, namely: configuring a control unit housing a control section and a power source section and a panel unit housing a radiation detection panel as separate bodies, and rotatably connecting one edge portion of each of the control unit and the panel unit together with a connection member, so as to adopt two states, a closed state in which one face of the control unit faces one face of the panel unit, and an open state in which the one face of the control unit and the one face of the panel unit are side-by-side and face in substantially the same direction.
However, in such a case, in the open state the other face of the panel unit (the face that faces downwards) is sometimes positioned above the other face of the control unit (the face that faces down). In such a case, if image capture is performed in a state in which the investigation subject is placed on top of the radiographic imaging apparatus, then new problems sometimes arise, such as load from the investigation subject resulting in distortion of the panel unit, leading to the images obtained by image capture being distorted, and even leading to breakage of the radiation detection panel.
Namely, the radiation detection panel can be formed by a glass substrate, similarly to a liquid crystal display, and can be made comparatively thin. However, circuit elements employed in the control unit, such as an inductance circuit, coil, or the like, and a battery and the like employed in the power source section, often have a height that is higher than that of the radiation detection panel. In such cases, as a result of making the panel unit thinner than the control unit, there is a high possibility that the bottom face of the panel unit is positioned above the bottom face of the control unit.
In order to realize an electronic cassette of the shape and size (thickness about 16 mm) that can be set in an imaging stage or the like similar to that of existing film cassettes, inevitably the thicknesses of the panel unit and the control unit are different, with the panel unit required to be as thin as possible. Furthermore, in order to suppress an unpleasant feeling of an investigation subject, heat generating portions, such as the control section and the power source section, are housed in the control unit wherever possible, and the panel unit inevitably becomes thinner by a corresponding amount. As the size of any gap between the outer surface of the panel unit and the radiation detection panel surface increases, the distance between the imaging subject and the radiation detection panel increases, and since this leads to blurring of the images this gap should be made as small as possible. As a result the panel unit inevitably become thinner. In such cases too, as a result of the panel unit being relatively thinner than the control unit, there is a high possibility that the bottom face of the panel unit is positioned higher than the bottom face of the control unit.